Internal combustion engines, particularly the internal combustion engines in motor vehicles, contribute a substantial amount of exhaust products to the atmosphere including substantial amounts of the oxides of nitrogen, hydrocarbons and carbon monoxide which are discharged from such engines in the exhaust gases. These pollutants when introduced into the atmosphere in sufficient quantities produce an atmospheric condition referred to as air pollution or smog.
Exhaust manifold gas temperatures will vary from 600.degree. F. to over 1800.degree. F. depending upon where the temperatures are measured and the engine operating conditions. If the exhaust gases are permitted to be retained in the manifold at the higher temperatures for a relatively short period of time, and mixed homogeneously with air, the unburned hydrocarbons and carbon monoxide in the exhaust gases will be oxidized to thus reduce the amount of such pollutants that are discharged from the manifold. However, with the manifold designs heretofore employed, the mass of the manifold prevents it from being brought up to a high temperature quickly to achieve such oxidation. Further, because of its mass, the manifold can not retain a large volume of the exhaust gases therein so that the gases are not retained therein for a period sufficient to achieve any significant degree of oxidation.
The present invention provides a means of obtaining a higher sensible exhaust gas temperature quickly and for increasing the dwell time of the gases in the manifold, thereby providing homogeneous mixing of the exhaust gases and air while at the same time providing a lightweight manifold construction which will be able to withstand its inherent expansion and contraction due to the elevated temperatures.[...]. caused by the oxidation of the smog-producing pollutants within the manifold.